A liquid crystal display device is widely used in products such as notebook computers and portable TVs. The liquid crystal display device generally includes a liquid crystal panel, and a backlight system to provide uniform collimated light to the liquid crystal panel. The backlight system mainly includes a light source and a light guide plate. A light emitting diode is widely used as the light source in the backlight system, due to its lower power consumption and high brightness. In a typical backlight system, a plurality of light emitting diodes is fixed on a flexible printed circuit and positioned adjacent the light guide plate.
At present, an operation mode of the flexible printed circuit with the light emitting diodes is normally one of two types: a series operation mode or a parallel operation mode. The type of operation mode is determined according to the requirements of the driving circuit of the light emitting diodes.
Referring to FIG. 3, one kind of light emitting diode flexible printed circuit 10 includes a plurality of light emitting diodes 11 and a plurality of first leads 13. The first leads 13 electrically interconnect the light emitting diodes 11 in turn such that make the light emitting diodes 11 are connected in series. An end one of the first leads 13 is electrically connected to a driving circuit (not shown) for providing driving voltage. Referring to FIG. 4, another kind of light emitting diode flexible printed circuit 20 includes a plurality of light emitting diodes 21, a second lead 23, and a plurality of third leads 25. The light emitting diodes 21 are interconnected in parallel between the second lead 23 and the third leads 25. The second lead 23 and the third leads 25 are connected to a driving circuit (not shown) for providing driving voltage.
The LED flexible printed circuit 10 that operates in series mode has a higher efficiency in utilization of electrical power, but is liable to be disturbed by electromagnetic interference (EMI). The LED flexible printed circuit 20 that operates in parallel mode has greater stability, but has a lower efficiency in utilization of electrical power. In some products, the backlight module employing a light emitting diode flexible printed circuit needs to be able to operate in either of the two modes, depending on the final destination of the product and the eventual end use of the product. For such products, it is commonplace to provide two sets of light emitting diodes with different operation modes on the one same flexible printed circuit. The designing and manufacturing of this kind of “hybrid” flexible printed circuit is troublesome, time-consuming, and costly.
Accordingly, what is needed is a light emitting diode flexible printed circuit that can overcome the above-described deficiencies.